title: Effect of different luting cements on fracture resistance in endodontically treated teeth.
abstract: BACKGROUND
  The aim of the present study was to evaluate the effect of three types of luting cements used for post cementation on the fracture resistance of endodontically treated maxillary premolars, restored with resin composite.
  
  
  METHODS
  One hundred intact single-rooted human maxillary premolars were randomly divided into 5 groups of 20 each. In groups 2-5, post spaces were prepared after root canal treatment and clinical crown reduction up to 1.5 mm above the CEJ. Teeth were divided in groups as follows: Group 1: intact teeth, Group 2: active prefabricated metallic posts (PMP), Group 3: PMP cemented with zinc phosphate luting cement, Group 4: PMP cemented with glass ionomer luting cement and Group 5: PMP cemented with resin luting cement. In groups 2-5 the teeth were restored with resin composite. Following thermocycling, the palatal cusp of each specimen was loaded to compression at an angle of 150˚ to its longitudinal axis at a strain rate of 2 mm/min until fracture occurred. Data were analyzed using one-way ANOVA and a post hoc Tukey test. Chi-square test was used for comparison of failure mode.
  
  
  RESULTS
  There were significant differences in fracture resistance between the test groups (P<0.001). The differences between group 2 with groups 1, 4 and 5 were statistically significant (P<0.05); whereas there were no significant differences in fracture resistance between the two other groups (P>0.05). Furthermore, there were no significant differences in the mode of failure between the 5 groups (P>0.05).
  
  
  CONCLUSIONS
  Zinc phosphate, glass ionomer and resin luting cements showed similar behaviors and achieved fracture resistance comparable to intact teeth. However, the use of active post (without cement) adversely affected the fracture resistance of root canal treated teeth.
authors.affiliation: Department of Operative Dentistry, Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Narmin
authors.initials: N
authors.lastname: Mohammadi
authors.forename: Amir Ahmad
authors.initials: AA
authors.lastname: Ajami
authors.forename: Soodabeh
authors.initials: S
authors.lastname: Kimyai
authors.forename: Mojdeh
authors.initials: M
authors.lastname: Rezaei Aval
keywords: Composite Resin; Endodontically Treated Teeth; Fracture Resistance; Luting Cement; Post